INTRAGENIC REGIONS REQUIRED FOR LAMB EXPORT
INTRAGENIC REGIONS REQUIRED FOR LAMB EXPORT
复制标题
DOI：
10.1073/pnas.81.12.3830
复制
发表时间：
1984-01-01
期刊：
影响因子：
--
通讯作者：
SILHAVY, TJ
中科院分区：
文献类型：
--
作者：
BENSON, SA;BREMER, E;SILHAVY, TJ
分离并表征了含有一系列lamB-lacZ融合体的大肠杆菌菌株。这些融合体中的每一种都指定了在NH 2末端具有LamB序列和β-CD的大的功能性COOH末端片段的杂合蛋白。半乳糖苷酶。存在于各种杂合蛋白中的LamB的量的范围从少至4个氨基酸到完整的信号序列（25个氨基酸）加上成熟蛋白的49个氨基酸。关于杂合蛋白输出，这些融合体分为3类。具有不完整LamB信号序列的杂合蛋白或具有完整信号序列加上≤成熟LamB蛋白的27个氨基酸不被输出并保留在细胞质中。融合菌株试图输出含有成熟LamB的完整信号序列加上39或43个氨基酸的杂合蛋白。这些蛋白质不局限于外膜。一个杂交蛋白，是稍大，含有49个氨基酸的自然LamB，被发现在外膜中的可观的量。这些融合体与先前描述的lamB-lacZ融合体一起，使得能够更精确地定义启动蛋白质输出过程所需的最小量的lamB。他们在基因上定位了一个信号，这个信号似乎引导LamB到达外膜。该信号位于其他主要外膜蛋白共享的氨基酸同源性区域内。
Escherichia coli strains containing a series of lamB-lacZ fusions were isolated and characterized. Each of these fusions specifies a hybrid protein with LamB sequences at the NH2 terminus and a large functional COOH-terminal fragment of .beta.-galactosidase. The amount of LamB present in the various hybrid proteins ranges from as few as 4 amino acids to a complete signal sequence (25 amino acids) plus 49 amino acids of the mature protein. With respect to hybrid protein export, these fusions fall into 3 classes. Hybrid proteins with an imcomplete LamB signal sequence or those that have a complete signal sequence plus .ltoreq. 27 amino acids of the mature LamB protein are not exported and remain in the cytoplasm. Fusion strains attempt to export hybrid proteins that contain a complete signal sequence plus 39 or 43 amino acids of mature LamB. These proteins are not localized to the outer membrane. A hybrid protein that is slightly larger, containing 49 amino acids of nature LamB, is found in the outer membrane in appreciable amounts. These fusions, together with previously described lamB-lacZ fusions, enabled more precise definition of the minimal amount of lamB required to initiate the process of protein export. They genetically locate a signal that appears to guide LamB to the outer membrane. This signal is within a region of amino acid homology shared by other major outer membrane proteins.